(a) Field of the Invention
The present invention relates to an environmentally friendly vehicle. More particularly, the present invention relates to a system and method for detecting engine clutch delivery torque of an environmentally friendly vehicle which can improve drivability and fuel consumption by detecting delivery torque of an engine clutch.
(b) Description of the Related Art
Environmentally friendly vehicles improve fuel consumption and comply with recent exhaust regulations. The environmentally friendly vehicle, generally includes a fuel cell vehicle, electric vehicle, a plug-in electric vehicle, and a hybrid vehicle equipped with one or more motors and engines, a battery storing high voltage electricity for operating the motor, an inverter that converts the DC voltage of the battery into AC voltage, and an engine clutch disposed between the engine and the motor to transmit the power of the engine to a driving shaft.
The environmentally friendly vehicle may operate in an HEV (hybrid electric vehicle) driving mode or an EV driving mode (electric vehicle) by engaging/disengaging the engine clutch according to the intention of the driver operating the acceleration pedal and the brake pedal, the load, the vehicle speed, and the SOC (Status Of Charge) of the battery.
It is possible to ensure drivability of the environmentally friendly vehicle by engaging the engine clutch after the engine speed and the motor speed are synchronized to maintain a constant torque during power transmission between the engine and the motor, when changing from the EV mode to the HEV mode.
However, it is necessary to control the engine clutch to slip for starting under conditions when the battery is maintained in a low SOC, when the temperatures of the battery and the motor is above a reference temperature condition, and when the road that the vehicle travels on has a steep slope. Additionally, it is necessary to control the pressure of the clutch to control the engine clutch to slip under the driving conditions.
The delivery torque of the engine clutch, which is torque (e.g., load at both ends of the engine clutch) transmitted by physical contact between the friction surfaces of both ends of the engine clutch, can be estimated from the efficient pressure of the friction coefficient.
Controlling the engine clutch is an important factor that determines the drivability and the fuel consumption in starting the environmentally friendly vehicle, the friction coefficient changes with the deviation in current and pressure characteristics of a solenoid valve operating the engine clutch, aging of the solenoid valve, and degradation of the friction members at both ends of the engine clutch, generating characteristic deviations.
As described above, it is difficult to precisely control the engine clutch in the environmentally friendly vehicle, because characteristic deviations are generated by deterioration of the parts associated with the control of the engine clutch, thereby decreasing drivability and fuel consumption.
Characteristic deviations are generated in the estimated delivery torque, depending on the types of the vehicles, because a technology of detecting the delivery torque of the engine clutch is not applied to the environmentally friendly in the related art, so the acceleration characteristic of starting may be different according to the vehicle type and in durability (aging).
Further, in controlling the engine speed and the responsiveness for the starting is deteriorated, and incorrect factors may be fed forward to the engine controller when controlling the engine clutch in starting.
The above information disclosed in this section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.